|Publication number||US7359369 B2|
|Application number||US 10/209,052|
|Publication date||Apr 15, 2008|
|Filing date||Jul 30, 2002|
|Priority date||Jul 30, 2002|
|Also published as||CA2493501A1, CN1672366A, CN100505656C, DE60318209D1, DE60318209T2, EP1525715A1, EP1525715B1, US20040022241, WO2004012398A1|
|Publication number||10209052, 209052, US 7359369 B2, US 7359369B2, US-B2-7359369, US7359369 B2, US7359369B2|
|Inventors||Scott Anthony Boynton, Alex Urquizo, Vincent Todd Grove|
|Original Assignee||Cisco Technology, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (16), Non-Patent Citations (2), Referenced by (3), Classifications (7), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This disclosure relates to modem relay, more particularly to modem relay devices that combine egress gateways and remote access servers.
The International Telecommunications Union (ITU) is in the process of approving a new standard for modem sessions over packet networks, referred to as modem over Internet Protocol (V.MoIP). It must be noted that this standard may actually apply to all packet networks, not just IP.
Modem relay terminates the physical layer and link layer error correction/detection protocol at the ingress gateway and may send compressed data over a packet network to an egress gateway. The first leg of the call occurs between the modem and the ingress gateway, where the modem signals are converted to packets. The second leg of the call sends the packets across the data network to the egress gateway. The final leg of the call, between the egress gateway and the remote access server, remodulates the packet data back into modem signals and sends the modem signals to the remote access server.
Typically, the egress gateway terminates the physical layer at the gateway and has a processor that handles the remodulation and connection between the egress gateway and the remote access server.
One embodiment of the invention is a network device having at least one port to receive modem over network signals. A router routes data associated with the modem over network signals received from an aggregator. The aggregator uncompresses the modem over network signals and send the data associated with the signals to the router directly.
Ingress gateways communicating with the network device negotiate with the client modem without waiting for modem response tones from the network device. The ingress gateway has either already identified the network address to which the modem is trying to connect to be a such a network device, or it is informed of that during call setup. The ingress gateway then routes data associated with the call to the network device.
The network device receives signals indicating that there is an incoming modem over data network call and communicates with the ingress gateway. The network device then routes the data as if it were a remote access server.
The invention may be best understood by reading the disclosure with reference to the drawings, wherein:
An example of a network capable of transmitting modem signals over a network in accordance with the prior art is shown in
The ingress gateway 12 accepts the modem tone signals and converts them to packet data and transmits them across the network 14 to the egress gateway 16. Egress gateway 16 then reconverts the data back into modem tones via remodulation and transmits those tones to the remote access server (RAS) 18. The process is then performed in the reverse direction to facilitate call setup and negotiation between the modem 10 and the remote access server (RAS) 18.
In the ITU standard for Modem Relay, currently under development, the physical layer and link layer error correction/detection protocol are terminated at the ingress gateway. The egress gateway may perform error correction/detection and remodulate the data into the modulated tones necessary for communication with the RAS 18.
In an alternative embodiment of current implementation in accordance with the prior art, the egress gateway and the remote access server are combined into one device referred to as a modem relay aggregator (MRA) 20. The MRA 20 has a digital signal processor 22 that generates and provides the modem response tones necessary to communicate with the client modem 10. However, it is possible to provide an MRA that does not require a digital signal processor, or any modem physical layer negotiation with the client modem.
As can be seen in
In either case, if the ingress gateway has the information that the end of the connection is an MRA, the ingress gateway 32 can localize the modem negotiation and negotiate with the client modem 30 without receiving any modem response tones from the MRA 36. Once the modem negotiation is completed, the ingress gateway would route the information to the MRA 36 via the network 34 as if the MRA were now the RAS to which the client modem was trying to connect. The MRA would then route the data coming from the client modem, functioning as an RAS. For purposes of the discussion here, this data will be referred to as ‘data associated with the modem over network call,’ as the data being routed by the MRA in the capacity of an RAS is coming from a client modem that ‘thinks’ it is connected to a RAS as in the prior art implementation such as that of
In this manner, there is no need for the MRA to generate modem response tones, and therefore no need for a DSP in the MRA. In addition to this simplification of the device, the MRA functioning without the modem response process eliminates any delays or packet drops that may occur during call discrimination or initial modem training. This may also provide faster modem connections, as there is only one modem connection in the circuit established between the modem 30 and the MRA 36.
One embodiment of a process to connect a call at the MRA is shown in flowchart form in
If the ingress gateway does not already understand that the egress gateway/RAS combination has been replaced by an MRA, or that the MRA will not be providing modem response tones, the MRA may send an identification signal at 42 that informs the ingress gateway of the nature of the MRA. This will then cause the ingress gateway to perform the modem negotiation without waiting for modem response tones from the MRA or the RAS. Once the call setup has been completed, the ingress gateway and the MRA may optionally negotiate call parameters such as optimal data compression parameters at 44. The MRA then begins routing data from the client modem, functioning in the capacity of a RAS, at 46.
One embodiment of a process to connect a call using an MRA from the ingress gateway is shown in
However, neither of these two processes is necessary. The ingress gateway may already realize that the RAS to which the modem is attempting to connect is an MRA and may start modem negotiation at 56, without any determination of an appropriate MRA. Once the modem negotiation is complete, the ingress gateway routes the data associated with the call to the MRA at 58. The MRA would then function as the RAS and route the data accordingly. All of this is done without the use or need for a DSP, which will be referred to as routing the data directly.
The DSP can be replaced by a less expensive solution such as an FPGA (field programmable gate array) or a general-purpose processor such as a RISC (reduced instruction set) processor. The advantage of the FPGA is that it could implement in hardware the well-defined algorithms, which perform data compression such as V.42bis, and V.44, and create a solution that is faster than a DSP, supports more sessions and is less expensive. The advantage of the general-purpose processor such as a RISC processor is that it is a less expensive method to terminate the PPP protocol stack.
As can be seen in
When the call is first brought up, the channel is considered a VoIP (Voice over IP) call. The channel is in Audio mode and it uses RTP (Real Time Transport Protocol). The V.MoIP standard specifies two methods to transport modem signals across the packet network. One is Modem Relay that uses a different transport protocol called SPRT (Simple Packet Relay Transport). Therefore, Modem Relay has a different protocol stack using SPRT even though it uses the same VoIP channel. The second method is call VBD (voice band data) where the channel uses RTP and modem signals are transported across the packet network using a codec suitable for modem signals such as under G.711. So VBD is similar to Audio Mode. However, certain special voice setting need to be used in order to transport modem signals reliably, such as using a fixed jitter buffer. In essence, Modem Relay uses the same infrastructure as a VoIP call, but uses a different transport protocol optimally designed to carry modem signals across a packet network.
In the example where a VoIP channel is used to carry on signals in the VBD mode the modem signals are not terminated at the gateways. The gateways transport the modem signals as they are across the VoIP channel using RTP protocol. If Modem Relay is used the physical and Link Layer error corrections are terminated at the gateway. The gateway then uses the protocol SPRT to carry on the modem data across the packet network.
A second port 68 may be used for communication with the network for routing the data associated with the modem over data network call. In actuality, it may be the same port, but for ease of understanding, they are shown as two separate ports here. The aggregator 64 is operable to receive the modem over network signals and terminate the modem or voice call, and then pass the data associated with that call to the router 66 directly, without any modem negotiation. The router then routes the data accordingly. In terminating the call, the aggregator does not responds to the modem signals, as would an MRA with a DSP, but instead may send the signal that indicates that the ingress gateway should handle that activity, if necessary.
During call setup, the aggregator 64 may communicate with the ingress gateway to exchange control signals, beyond any signals sent to identify the device as an MRA. These may be performed using in-band signaling, H.323 or H.248 Megaco format messages, media gateway control protocol (MGCP) messages, or session initiation protocol (SIP) messages, as examples. The aggregator may be a field-programmable gate array (FPGA), or an application specific integrated circuit (ASIC), as examples.
The elimination of the DSP at the MRA provides simplified requirements for the network device hardware, which may in turn lead to lower costs. As mentioned earlier, the elimination of the modem negotiation signals required by current implementations of the MRA eliminates the possibility of delays and packet drops during call setup, making the connection complete faster.
Thus, although there has been described to this point a particular embodiment for a method and apparatus for a modem relay aggregator, it is not intended that such specific references be considered as limitations upon the scope of this invention except in-so-far as set forth in the following claims.
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|U.S. Classification||370/352, 370/522, 370/395.2|
|International Classification||H04L12/66, H04L12/28|
|Jul 30, 2002||AS||Assignment|
Owner name: CISCO TECHNOLOGY, INC., CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BOYNTON, SCOTT ANTHONY;URQUIZO, ALEX;GROVE, VINCENT TODD;REEL/FRAME:013161/0058;SIGNING DATES FROM 20020725 TO 20020729
|Oct 17, 2011||FPAY||Fee payment|
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